The use of dietary supplements and vitamin consumption during and after the Covid pandemic in Vietnam: a perspective of user-generated content

The study situates the surge in vitamin and dietary supplement (DS) interest among Vietnamese consumers within the COVID-19 pandemic, during which social isolation, heightened health anxiety, and increased online shopping and social media use were prevalent. Vietnamese consumers often rely on Facebook for information and peer experiences to inform DS purchases but face uncertainty about product efficacy and safety. The research addresses gaps linking UGC characteristics to DS purchase intention in a sensitive health crisis context. It poses two main questions: (1) What are the key predictors, grounded in the heuristic–systematic model (HSM), of intention to use vitamins and DS during and post-pandemic? (2) How does health-related information on social media affect behavioral intention toward supportive health products? The study is theoretically grounded in the Theory of Reasoned Action (TRA), Source Credibility Theory, and the HSM, focusing on heuristic routes (lower-effort, non-content cues) and trust in the absence of strong institutional safeguards, to explain how UGC influences consumer intentions for health-protective products during and after COVID-19.

The literature review covers: (1) User-Generated Content (UGC): Defined by public availability, creativity, and being outside professional routines. UGC, seen as more credible than firm-generated content, strongly influences purchase intention across platforms (YouTube, Facebook, apps), with consumers relying on peer reviews to evaluate products. UGC is particularly impactful in green/health contexts and Vietnamese online commerce. (2) Heuristic–Systematic Model (HSM): A dual-process framework where heuristic (cue-based) and systematic (comprehensive) processing may operate in parallel to shape judgments and decisions, widely applied in healthcare information contexts. Message- and source-level characteristics both influence decisions; heuristic processing can be especially influential during crises. (3) Consumer purchase intention: An antecedent of actual behavior, shaped by multiple online factors including perceived value, trust, eWOM, and UGC. COVID-19 has shifted intentions toward online purchasing, including health-related products. Main UGC elements and hypotheses: Hedonic value (emotional enjoyment) may or may not drive purchase intention (H1). Utilitarian value (functional usefulness) is expected to positively influence intention (H2). Information quality (understandability, relevance, sufficiency) is expected to increase intention (H3). Trust in UGC is critical for intention and may be influenced by hedonic (H4) and utilitarian values (H5), with trust positively affecting purchase intention (H6). The proposed model links Hedonic Value, Utilitarian Value, and Information Quality to Trust and Purchase Intention for vitamins and DS on Facebook.

Design: Cross-sectional survey using a structured online questionnaire distributed via Google Forms with convenience sampling. Target participants had stable living standards, health-conscious lifestyles (e.g., DS use), exposure to UGC (reviews, posts, videos), and used Facebook to inform purchases. Screening ensured experience with Facebook product reviews and awareness of vitamins/DS during COVID-19. Measures: All constructs used established scales, rated on 5-point Likert (1=strongly disagree to 5=strongly agree). Hedonic Value (5 items) from Gan & Wang (2017), Sethna et al. (2017); Utilitarian Value (5) from Hazari et al. (2017), Sethna et al. (2017); Information Quality (5) from Hazari et al. (2017), Kim et al. (2012); Trust (5) from Chari et al. (2016), Hazari et al. (2017); Purchase Intention (5) from Hazari et al. (2017), Sethna et al. (2017). A pilot with expert review and 20 Facebook users refined items for clarity and content validity. Sample: 331 Vietnamese respondents from Northern, Central, and Southern regions; 323 reported engaging with Facebook reviews; 1 among them not aware of related health products via social media. Demographics included: age mostly 20–29 (72.8%) and 30–39 (19%); 65.9% female; income primarily 5–10 million VND (44.7%) and above 10–15 million VND (29%); residence: Southern (61.3%), Northern (28.7%), Central (10%). Analysis: Structural Equation Modeling (SEM) using a two-step approach (measurement and structural models). EFA verified dimensionality; CFA tested reliability and validity (Cronbach’s alpha, Composite Reliability (CR), Average Variance Extracted (AVE)); discriminant validity evaluated via AVE/MSV comparisons and square roots of AVE. Model fit assessed with χ²/df, GFI, CFI, RMSEA. Mediation tested via bootstrapping (2,000 samples, 95% bias-corrected CI).

Measurement model: Bartlett’s test p=0.000; KMO=0.855 indicating sampling adequacy. EFA yielded four factors with eigenvalues ≥1 explaining 69.2% of variance. CFA showed adequate loadings (>0.5), with highest 0.956 (Trust item) and lowest 0.544 (Information Quality item). Reliability: Cronbach’s alpha 0.854–0.911; CR 0.858–0.912; AVE 0.549–0.674, supporting convergent validity and internal consistency. Discriminant validity criteria met. Model fit: χ²/df=2.847 (<3), χ²=746.113, GFI=0.855, CFI=0.907, RMSEA=0.075, indicating acceptable to good fit. Structural paths (standardized estimates): - Information Quality → Purchase Intention: 0.418, p<0.001 (significant) - Utilitarian Value → Purchase Intention: 0.250, p<0.001 (significant) - Trust → Purchase Intention: 0.266, p<0.001 (significant) - Hedonic Value → Purchase Intention: 0.052, p=0.245 (not significant) - Utilitarian Value → Trust: 0.331, p<0.001 (significant) - Hedonic Value → Trust: 0.142, p=0.020 (significant) Mediation (bootstrapping): - Hedonic Value → Trust → Purchase Intention: indirect effect=0.039, p=0.025, full mediation (direct path non-significant). - Utilitarian Value → Trust → Purchase Intention: indirect effect=0.095, p=0.001, partial mediation (direct path significant). Overall: Quality, Utilitarian Value, and Trust positively predict purchase intention for vitamins/DS on Facebook; Hedonic Value does not directly predict intention during/post-pandemic. The abstract also notes Quantity of UGC as positively related to intention (though not modeled in the reported SEM results).

Findings support that during a public health crisis, consumers prioritize cognitive and functional aspects of UGC (information quality, utilitarian value) and trust, which significantly drive purchase intention for vitamins and dietary supplements. Hedonic value enhances trust but does not directly translate into purchase intention in this context, suggesting diminished emphasis on enjoyment/playfulness when health risks are salient. The results align with prior work linking information quality and utilitarian benefits to behavioral intentions and trust in online environments, and they extend HSM by showing how heuristic cues (perceived values, trust) and message validity (quality) jointly shape intentions in health-related purchases. The mediation results highlight trust as a key mechanism, fully mediating hedonic effects and partially mediating utilitarian effects on intention. These patterns suggest that, amid and after COVID-19, Vietnamese consumers rely on useful, credible peer-generated content rather than affective enjoyment to reduce uncertainty and inform DS purchase decisions.

This study contributes theoretically by integrating TRA, Source Credibility Theory, and HSM to explain how UGC attributes shape purchase intentions for vitamins and dietary supplements during and after COVID-19. It evidences that information quality and utilitarian value, via trust, are primary drivers of intention, while hedonic value exerts an indirect influence through trust. Practically, brands and marketers should prioritize fostering high-quality, objective, and sufficient user content, encourage reviews/ratings, broaden presence beyond Facebook to video-centric platforms (e.g., TikTok, Instagram), and cultivate relationships that build trust and perceived usefulness. Future research should broaden product categories (e.g., functional foods), expand beyond Vietnam to test generalizability across regions and cultures, and incorporate additional UGC factors (health-related, cultural, personality dimensions), perceived risk and knowledge, and the role of livestreaming shoppable platforms.

- Product scope: Focused on dietary supplements; may not generalize to other health product categories (e.g., functional foods). Future work should examine broader or more specific product types within health/DS. - Geography/sample: Vietnam-only convenience sample (n=331) limits generalizability to wider Asian or global populations. - Construct scope: Only selected UGC factors (hedonic, utilitarian, information quality, trust) were examined; other relevant dimensions (health-related, cultural, personality factors, perceived risk/knowledge, livestreaming contexts) were not included. - The abstract mentions UGC quantity, but the reported SEM focused on information quality, utilitarian/hedonic values, and trust; future studies should explicitly model and test quantity effects.